bims-miptne 2025-06-22 papers

Basic Res Cardiol. 2025 Jun 19.

The innate immune receptor NLRX1 is a novel required modulator for mPTP opening: implications for cardioprotection.

NLRX1 is the only NOD-like innate immune receptor that localises to mitochondria. We previously demonstrated that NLRX1 deletion increased infarct size in isolated mouse hearts subjected to ischemia-reperfusion injury (IRI); however, underlying mechanisms are yet to be identified. Given the crucial role played by mitochondria in cardiac IRI, we here hypothesise that NLRX1 affects key mechanisms of cardiac IRI. Cardiac IRI was evaluated in isolated C57BL/6J (WT) and NLRX1 knock out (KO) mouse hearts. The following known modulators of IRI were explored in isolated hearts, isolated mitochondria; or permeabilised cardiac fibres: 1) mTOR/RISK/autophagy regulation, 2) AMPK and mitochondrial energy production, and 3) mitochondrial permeability transition pore (mPTP) opening. NLRX1 deletion increased IRI, and cardiac NLRX1 was decreased after IRI in mouse and pig hearts. NLRX1 ablation caused decreased mTOR and RISK pathway (Akt, ERK, and S6K) activation following IR, without affecting autophagy/inflammation/oxidative stress markers. The RISK activator Urocortin dissipated NLRX1 effects on mTOR, RISK pathway and IRI, indicating that increased cardiac IRI with NLRX1 deletion is, at least partly, due to impaired RISK activation. The energy sensor AMPK was activated in NLRX1 KO hearts, possibly due to slowed mitochondrial respiratory responses (impaired mitochondrial permeability) towards palmitoylcarnitine in permeabilised cardiac fibres. NLRX1 deletion completely abolished calcium-induced mPTP opening, and cyclosporine A (CsA) effects on mPTP, both before and after IR, and was associated with increased mitochondrial calcium content after IR. Mitochondrial sub-fractionation studies localised NLRX1 to the inner mitochondrial membrane. NLRX1 deletion associated with decreased phosphorylation of mitochondrial Got2, Cx43, Myl2, Ndufb7 and MICOS10. The mPTP inhibitor CsA abolished IRI differences between KO and WT hearts, suggesting that the permanent closure of mPTP due to NLRX1 deletion contributed to the increased IR sensitivity of NLRX1 KO hearts. This is the first demonstration that the mitochondrial NLRX1 is a novel factor required for mPTP opening and contributes to cardioprotection against acute IRI through RISK pathway activation and prevention of permanent mPTP closure.

Keywords: AMPK; I/R injury; Mitochondria; Mitochondrial transition pore opening; NLRX1; RISK pathway

DOI: https://doi.org/10.1007/s00395-025-01124-x

Acta Biomater. 2025 Jun 16. pii: S1742-7061(25)00416-7. [Epub ahead of print]

Nano-carriers mediate reciprocally chained promotion between ROS and mitochondrial calcium overload for enhanced antitumor therapy.

Zhihao Zhao, Ke Ling, Jun Yan, Zhexiang Wang, Chuntao Chen, Dongping Sun, Jian Liu.

Calcium ions (Ca²⁺) and reactive oxygen species (ROS) play pivotal roles in cellular signaling and the regulation of diverse biological processes. Complex and dynamic interactions between Ca²⁺ and ROS signaling pathways are often exploited by tumor cells to resist therapeutic interventions. In this study, we present a strategy of cancer treatment based on the reciprocally reinforcing interplay between ROS burst and mitochondrial calcium overload. The major components of our nano carriers integrate CaCO3 nanoparticles loaded with glucose oxidase (GOx), and copper peroxide nanodots (CPDs) in a DSPE-S-S-PEG-modified liposomal format (abbr. GCCL,). This hybrid nanosystem is designed to facilitate controlled and accelerated release of Ca²⁺ and ROS, thereby establishing dual positive feedback loops that amplify both mitochondrial calcium accumulation and oxidative stress. By harnessing this synergistic cycle, our platform enhances the efficacy of chemodynamic therapy and calcium-induced mitochondrial damage, offering a promising strategy for translational cancer treatment. STATEMENT OF SIGNIFICANCE: Here we report a strategy of antitumor therapeutic by designing a dual positive feedback loop of pH-driven self-accelerated Ca2+ and H2O2 release, thus reciprocally promoting ROS production and mitochondrial calcium overload for tumor eradication. After cellular uptake of GCCL, releasing of the cargos inside the liposomes can introduce a cascade of chemical reactions and biochemical cues, leading to calcium overload and ROS burst. These two major effects are mutually linked with each other, which is utilized by our GCCL design to fuel the positive feedback loops for tumor cell apoptosis in vitro and effective cancer ablation in vivo. Our nano therapy stands out with improved tumor suppression, with a lower dosage of copper element in the treatments of 4T1 xenograft tumor-bearing BALB/c mice model.

Keywords: Chemodynamic therapies; Mitochondria calcium overload; Nanocarriers; Reactive oxygen species; Reciprocally chained promotion

DOI: https://doi.org/10.1016/j.actbio.2025.06.009

Mol Cells. 2025 Jun 12. pii: S1016-8478(25)00062-7. [Epub ahead of print] 100238

Analysis of mitochondrial membrane potential, ROS, and calcium.

Hye-Kyung Park, Byoung Heon Kang.

Mitochondria play a central role in cellular energy metabolism and signaling, and their dysfunction is associated with a wide range of diseases. Therefore, assessing mitochondrial function is essential for understanding their role in various cellular processes and disease progression. Here, we describe the principles and methodologies for analyzing mitochondrial membrane potential, reactive oxygen species, and calcium levels using the fluorescent probes TMRM, MitoSOX, and Rhod-2AM, respectively. This work provides a practical guide for researchers investigating mitochondrial function under physiological and pathological conditions.

Keywords: Calcium; MitoSOX; Mitochondria; ROS; Rhod-2AM; TMRM; membrane potential

DOI: https://doi.org/10.1016/j.mocell.2025.100238

Toxicology. 2025 Jun 13. pii: S0300-483X(25)00180-5. [Epub ahead of print]517 154221

Iron supplementation switches mode of cell death to ferroptosis during acetaminophen-induced liver injury in mice rendering it resistant to N-acetylcysteine.

Olamide B Adelusi, Aparna Venkatraman, Jephte Y Akakpo, Anup Ramachandran, Hartmut Jaeschke.

Acetaminophen (APAP) overdose can cause liver injury and is the leading cause of acute liver failure in Western countries. Hepatocellular necrosis induced by APAP involves the formation of a reactive metabolite, triggering mitochondrial oxidant stress and peroxynitrite formation. Iron-catalyzed protein nitration is critical for mitochondrial dysfunction and cell death in the absence of lipid peroxidation (LPO). However, co-treatment of APAP and ferrous sulfate aggravated protein nitration and liver injury but also triggered extensive LPO (measured as malondialdehyde and hydroxy eicosatetraenoic acid (HETE) species). The objective of this study was to evaluate whether the aggravated injury under these conditions is caused by a combination of protein nitration and LPO or if LPO is now the dominant injury mechanism. To test this, C57BL/6 J mice were co-treated with APAP (300 mg/kg) and a moderate dose of ferrous sulfate (0.15 mmol/kg) for 6 h. Some animals also received a dose of Mito-TEMPO, the mitochondria-targeted SOD mimetic, or minocycline, an inhibitor of mitochondrial iron uptake. Although Mito-TEMPO and minocycline eliminated protein nitration and liver injury after APAP alone, these interventions did not affect LPO and only had a moderate effect on protein nitration and liver injury in the APAP+Fe2+ group, suggesting LPO as the main mechanism of cell death. Consistent with these findings, delayed treatment with clinically relevant antidotes N-acetylcysteine and fomepizole did not reduce LPO or liver injury. Thus, liver injury after APAP+Fe2+ is no longer primarily driven by mitochondrial oxidant stress and peroxynitrite-mediated necrosis but by lipid peroxidation and a ferroptosis-like cell death.

Keywords: 4-methylpyrazole; N-acetylcysteine; drug hepatotoxicity; ferroptosis; lipid peroxidation; peroxynitrite

DOI: https://doi.org/10.1016/j.tox.2025.154221

Cell Mol Life Sci. 2025 Jun 14. 82(1): 238

Resting Ca2+ fluxes protect cells from fast mitochondrial fragmentation, cell stress responses, and immediate transcriptional reprogramming.

Caroline Fecher, Annemarie Sodmann, Felicitas Schlott, Juliane Jaepel, Franziska Schmitt, Isabella Lengfelder, Thorsten Bischler, Bernhard Nieswandt, Konstanze F Winklhofer, Robert Blum.

Homeostatic calcium ion (Ca2+) fluxes between the endoplasmic reticulum, cytosol, and extracellular space occur not only in response to cell stimulation but also in unstimulated cells. Using murine astrocytes as a model, we asked whether there is a signaling function of these resting Ca2+ fluxes. The data showed that endoplasmic reticulum (ER) Ca²⁺ depletion, induced by sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA) inhibition, resulted to prolonged Ca²⁺ influx and mitochondrial fragmentation within 10 to 30 min. This mitochondrial fragmentation could be prevented in Ca2+-free medium or by inhibiting store-operated Ca2+ entry (SOCE). Similarly, attenuation of STIM proteins, which are vital ER Ca2+ sensors, protected mitochondrial morphology. On the molecular level, ER Ca2+ depletion, achieved either by removing extracellular Ca2+ or through acute SERCA inhibition, led to changes in gene expression of about 13% and 41% of the transcriptome within an hour, respectively. Transcriptome changes were associated with universal biological processes such as transcription, differentiation, or cell stress. Strong increase in expression was observed for the transcription factor ATF4, which is under control of the kinase PERK (EIF2AK3), a key protein involved in ER stress. Corroborating these findings, PERK was rapidly phosphorylated in Ca2+-free medium or after acute pharmacological inhibition of SOCE. In summary, resting, homeostatic Ca2+ fluxes prevent immediate-early cell stress and transcriptional reprogramming.

Keywords: Calcium signaling; ER calcium; ER calcium leak; Mitochondrial fragmentation; Resting calcium fluxes; Store-operated calcium entry; Transcriptome changes

DOI: https://doi.org/10.1007/s00018-025-05745-2

Hepatobiliary Pancreat Dis Int. 2025 Jun 06. pii: S1499-3872(25)00097-9. [Epub ahead of print]

Novel drug targets for the early treatment of acute pancreatitis: Focusing on calcium signaling.

Jin-Hao Chen, Robert Sutton, Li Wen.

Acute pancreatitis (AP) is a common but potentially devastating disease characterized at onset pathophysiologically by premature activation of digestive enzymes within the pancreas. Despite an abundance of preclinical research and, until recently, a series of disappointing clinical trials, no specific disease modifying pharmacological treatment has yet been approved for this condition. Recent novel approaches to understanding the molecular pathogenesis of AP provide us with renewed optimism for translational drug discovery. Although digestive enzyme activation is the hallmark of AP, a critical mechanism that initiates AP is intracellular calcium (Ca2+) overload in pancreatic parenchymal cells, which triggers mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and impairs autophagic flux. These processes are pivotal to the disease and present a range of drug targets, associated with the inflammatory responses that drive local and systemic inflammation in AP. Progress in translation has now been made, targeting the ORAI channel with the inhibitor zegocractin (Auxora) to reduce pancreatic injury and inflammatory responses in human AP. Herein we evaluated potential drug targets for the early treatment of AP, focused on intra-acinar mechanisms of injury central to the onset and severity of AP. Our analysis highlights the opportunities and progress in translating these molecular insights into clinical therapies.

Keywords: Acute pancreatitis; Autophagy; Calcium; Drug targets; Endoplasmic reticulum stress; Mitochondria

DOI: https://doi.org/10.1016/j.hbpd.2025.06.001